1. Field of the Invention:
The present invention relates generally to apparatus and methodology for discharging static electricity from a vehicle and, more particularly, to avoiding wear and tear on the electrical conductor which discharges the static electricity to ground.
2. Description of Prior Art:
Static electricity buildup is a fundamental phenomenon of nature, and we all have experienced it in one form or another. Static electricity varies widely in energy level, from a miniscule level where one barely notices an annoying spark at the end of one's finger as one touches a metal object in a dry environment after walking across a carpet, all the way up to the highly dramatic and dangerous lightning flashes during a summer thunderstorm. Both are examples of static electricity discharge.
Static electricity is a bigger problem in dry climates such as the southwest U.S. than in humid climates such as the northeast U.S., because water vapor in places of high humidity forms a natural leakage path for the static electricity. All motor vehicles, trucks, cars, buses etc., can build up static electricity charge relative to ground because their rubber tires can act as insulators between the body of the vehicle and Earth.
Under the wrong conditions, motor vehicle static electricity discharge can be a hazardous event. For example, if a gasoline tanker truck builds up static charge and somehow discharges that static electricity in the presence of fumes from the gasoline in the truck, then an enormous explosion may occur. It is, therefore, important to safely discharge static electricity from vehicles.
Most of us are familiar with the image of a gasoline tanker truck driving down the highway while dragging a steel chain behind, along the roadway. This is a prior art approach which discharges the static electricity while the truck is in motion because of the scraping of the electrically-conductive metal chain against the roadway. Referring to FIG. 1 (Prior Art) truck 100 is shown with truck body 101, front wheels 102 and rear wheels 103 supported by roadway 104. Truck body 101 has a metal chain 105 mounted from a conductive contact such as an axel located underneath the truck. The chain is shown to be in substantial contact with roadway 104. This contact is maintained regardless of whether the truck is in forward motion, is stopped, or is in reverse motion. This may be an effective way to reduce static electricity buildup, but it is only good if the chain is in contact with the roadway. At some point, after a long haul across the country, or after other excessive usage, road friction eventually causes the chain to wear out, and the effective discharge path to ground through the chain becomes intermittent or non-existent. When the truck driver exits the truck through door 106 there could be a static electricity discharge through that individual to ground, if the chain had worn away during transit, and if the driver touches the truck and ground at the same time which is very likely.
Also, there are other kinds of vehicles which can benefit from a safe static discharge path. The assignee of the present invention is a telecommunications company presently involved in installing a fiber to the premises (FTTP) infrastructure. The trucks used by the assignee's installers for this purpose contain a substantial amount of sensitive fiber splicing equipment and other sensitive equipment such as, e.g., line card installation equipment. All of this equipment can be very susceptible to, and negatively affected by, static electricity buildup. Thus, in addition to being a hazard to the technician installer who is driving the truck and who can, unknowingly, form a discharge path through his/her body from the truck to ground upon opening door 106 and setting foot on the ground while touching the truck, static electricity buildup can also wreak havoc with this sensitive equipment inside the truck.
Therefore, there is a need to always have a safe discharge path for static electricity in place from the truck to ground prior to any occupants in that truck opening the door to egress. This requires a technique for avoiding wear-out of the discharge path from road friction. Applicant provides such a technique with the present invention which addresses the problems noted in the prior art.